// Package metrics Prometheus 指标：进程内 registry + 文本端点（api 层按开关挂载 /metrics）。
//
// label 基数约束：channel/model 来自受管目录、status/kind 为有限枚举，可安全做 label；
// 请求级随机值（trace id、用户 id、错误详情）禁止入 label，否则基数爆炸拖垮采集端。
package metrics

import (
	"net/http"

	"github.com/prometheus/client_golang/prometheus"
	"github.com/prometheus/client_golang/prometheus/collectors"
	"github.com/prometheus/client_golang/prometheus/promhttp"
)

var reg = prometheus.NewRegistry()

var (
	// RequestsTotal 代理请求终结计数。channel 为 "none" 表示未打到任何渠道
	// （无候选/满载等），model 为请求的模型名。
	RequestsTotal = prometheus.NewCounterVec(prometheus.CounterOpts{
		Name: "openteam_proxy_requests_total",
		Help: "Proxied requests terminated, by channel/model/status.",
	}, []string{"channel", "model", "status"})

	// RequestDuration 请求从进入 handler 到终结的耗时（按渠道）。
	RequestDuration = prometheus.NewHistogramVec(prometheus.HistogramOpts{
		Name:    "openteam_proxy_request_duration_seconds",
		Help:    "Proxy request duration, by channel.",
		Buckets: []float64{.05, .1, .25, .5, 1, 2.5, 5, 10, 30, 60, 120, 300},
	}, []string{"channel"})

	// ChannelFailures 上游失败计数（按渠道与失败类型），与运行期冷却同源。
	ChannelFailures = prometheus.NewCounterVec(prometheus.CounterOpts{
		Name: "openteam_channel_failures_total",
		Help: "Upstream failures, by channel/fail kind.",
	}, []string{"channel", "kind"})

	// RecorderQueueDepth 记账队列中待落库的记录数。持续增长说明 DB 写入跟不上。
	RecorderQueueDepth = prometheus.NewGauge(prometheus.GaugeOpts{
		Name: "openteam_usage_queue_depth",
		Help: "Usage records buffered, waiting to be flushed.",
	})

	// FrozenBalance 在途请求预扣（冻结）的金额合计（USD）。见 proxy 的 reserve/capture。
	FrozenBalance = prometheus.NewGauge(prometheus.GaugeOpts{
		Name: "openteam_frozen_balance",
		Help: "Balance reserved by in-flight requests (USD).",
	})
)

func init() {
	reg.MustRegister(
		RequestsTotal, RequestDuration, ChannelFailures, RecorderQueueDepth, FrozenBalance,
		collectors.NewGoCollector(),
		collectors.NewProcessCollector(collectors.ProcessCollectorOpts{}),
	)
}

// Handler /metrics 的 http.Handler（独立 registry，避免全局默认注册器的耦合）。
func Handler() http.Handler {
	return promhttp.HandlerFor(reg, promhttp.HandlerOpts{})
}